92 XJ Hard start, erratic idle, no rev under load

1992 2DR, 4.0 HO AW4

I was driving my Cherokee home from work the other day when it started stumbling, cutting out and backfiring out the manifold. I was able to limp it home but since then it has gotten so bad that it will barely move under its own power. Here's what I know so far:

-Hard start cold and hot. I have to crank much longer than usual to get it started

-Very erratic idle. From <500 rpm to >1500rpm

-Stumbles and backfires out the intake under throttle until above 1500 RPM

-Won't rev above 1000 RPM in drive even at WOT, stumbles, backfires and dies but much less severe in reverse

-Disconnecting the MAP sensor vacuum line from the manifold and blocking the fitting causes engine to run normally

-MAP sensor passes vacuum and voltage tests, swapping in known good sensor causes no change

- Computer throws trouble code 13: No change indicated between barometric pressure(Engine off) and manifold vacuum(Engine on)

-Crankshaft position sensor is round, three prong connector. I'm not sure exactly how to test this, as my Chilton only gives directions for testing the flat connectors.

I'm completely lost on what to do. The only advice any of my friends can give me is to throw money at it until it goes away, but I really don't want to spend money replacing parts until I know what is wrong, Any help would be greatly appreciated, and yes I have searched and am continuing to do so.

Hallo. I would say,begin by the ignition. Check plugs,wires,distrib.cap,rotor.Coil wire. Battery clamps.
Grounds of the engine to the firewall. Grounds by the battery. It's a start to begin.

p.s. fuelpressure on the line?. (schreader valve)


'92 XJ

Have you checked the vacuum orifice for the MAP? it may be plugged.

The manifold fitting, the vacuum line and the sensor are all clear and hold pressure.

Hallo. Maybe , you can clean your connector of the CPS by to pull it out and in a few times. No wiring against hot engine parts?